Mammographic screening: keeping women alive

Evaluation of: Tabár L, Vitak B, Chen TH et al. Swedish Two-County Trial: impact of mammographic screening on breast cancer mortality during 3 decades. Radiology 260(3), 658-663 (2011). In the 1980s, the periodic invitation of women aged 40-69 years for mammographic screening in the Swedish Two-County Trial showed a strong 30% reduction in breast cancer mortality. The result of 2-3-yearly mammographic examinations has persisted throughout the long follow-up of three decades. Through the richness of the collected and verified data, the trial has also demonstrated a substantial and absolute reduction in mortality risk. For each 414 women screened for 7 years (approximately four screening examinations), one breast cancer death was prevented. Transferring these outcomes to, for example, the national program of the UK, for every 1000 women aged 47-73 years attending the 3-yearly screenings (nine screening examinations) at least five to seven breast cancer deaths would be prevented. In recent follow-up papers by the Swedish trial group, the major human cost of screening (false-positive outcome, occurrence of interval cancer, overdiagnosis and radiation exposure) were judged to be in balance with the accurately demonstrated mortality benefit.